Power System

ABSTRACT

A power system is disclosed. The power system comprises a plurality of power supply units, a voltage sharing bus, and a current sharing bus. The sharing bus is used to transmit a sharing voltage, and the current sharing bus is used to transmit a first current reference value. Each of the power supply units comprises: a power converter, a feed-forward control (FFC) circuit, and a feedback control (FBC) circuit. The feed-forward control circuit is used to generate a second current reference value according to a difference between an input voltage of the power converter and the sharing voltage. The feedback control circuit is used to generate a current compensation value according to the second current reference value and the first current reference value. The power converter can adjusts the output current thereof in accordance with the current compensation value.

TECHNICAL FIELD

This invention relates to a power system, and more particularly, to apower system with sharing control and feed-forward control.

BACKGROUND ART

Recently, the characteristics of power electronic devices have beenimproved significantly. Power electronic devices with high-voltagerating, high-current rating, and high switching speeds have beendeveloped due to the improvement of semiconductor manufacturingtechniques. Power electronic devices are applied in electric powerequipment, such as switching power supplies, uninterruptible powersupplies, motor drivers, arc furnaces, trolley cars, battery chargers,lighting appliances etc. For example, converters are well known in thefield of electronics, such as DC-to-DC, DC-to-AC, AC-to-DC or AC-to-ACconverters. Such circuitry or devices are typically employed to convertone DC or AC voltage to another DC or AC voltage.

Typically, there are several kinds of power systems using theconverters, such as a central power system (CPS) or a distributed powersystem (DPS). Referring to FIG. 1, FIG. 1 is a system block diagramshowing a conventional central power system. In a central power system10, a single input power source 11 is electrically connected to a powerconverter 12 and then to a plurality of loadings (R_(L)) 13 (such aselectronic devices). For example, the input power source 11 may be a DCpower source, and the power converter 12 is employed to convert one DCvoltage level to another DC voltage level. Therefore, the input powersource 11 can supply power to the loadings 13. However, there are somedisadvantages in the conventional central power system, such as highcurrent stress on devices, poor reliability and difficulty in powermaintenance, etc.

Referring to FIG. 2, FIG. 2 is a system block diagram showing aconventional distributed power system. In the distributed power system,a single input power source 21 is electrically connected to a pluralityof DC-to-DC converters 22 and to a plurality of loadings (R_(L1),R_(L2), R_(L3)) 23 (such as electronic devices), wherein the DC-to-DCconverters 22 are electrically connected to the respective loadings 23,thereby supplying power to the loadings 23. Although there are someadvantages in the conventional distributed power system, such as lowercurrent stress on devices, supporting of N+1 redundancy, easemaintenance and customization with standardized module etc., yet whenthe single input power source 21 is broken-down or fails to supplypower, the whole distributed power system would be useless.

DISCLOSURE OF INVENTION Disclosure

Therefore, an aspect of the present invention is to provide a powersystem to feed-forward control the paralleling converters, therebyself-regulating the output status of each of the power sources.

Another aspect of the present invention is to provide a power systemwith a plurality of power sources and a plurality of converterselectrically connected thereto respectively in a one-to-one manner,thereby allowing each of the power sources to be replaceable.

According to an embodiment of the present invention, the power systemcomprises a voltage sharing bus and a plurality of power supply units.The power supply units are electrically connected in parallel and usedto provide power to a loading, wherein each of the power supply units iselectrically connected to the voltage sharing bus to receive a sharingvoltage transmitted by the voltage sharing bus, and comprises: a powerconverter, a resistor, a first comparator, a current detector, and asecond comparator. The power converter is electrically connected to apower source and the load. The resistor is electrically connected to aninput terminal of the power converter. The first comparator is used togenerate a current reference value in accordance with the differencebetween the sharing voltage and an input voltage of the power converter,wherein the first comparator is electrically connected to the resistorand the input terminal, and one end of the voltage sharing bus iselectrically connected between the resistor and the first comparator.The current detector is used to detect an output current value of thepower converter. The second comparator is used to generate the currentcompensation value in reference value thus that the power converteradjusts the output current value thereof in accordance with the currentcompensation value.

According to another embodiment of the present invention, the powersystem comprises a voltage sharing bus, a current sharing bus, and aplurality of power supply units. The power supply units are electricallyconnected in parallel and used to provide power to a loading, whereinthe power supply units are electrically connected to the voltage sharingbus to receive a sharing voltage transmitted by the voltage sharing busand electrically connected to the current sharing bus to receive a firstcurrent reference value transmitted by the current sharing bus, and eachof the power supply units comprises a power converter, a feed-forwardcontrol (FFC) circuit, and a feedback control (FBC) circuit. The powerconverter is electrically connected to a power source and the loading.The feed-forward control circuit is used to generate a second currentreference value in accordance with the difference between the sharingvoltage and an input voltage of the power converter, wherein one end ofthe voltage sharing bus is electrically connected to the feed-forwardcontrol circuit. The feedback control circuit is used to generate acurrent compensation value in accordance with the first currentreference value and the second current reference value, wherein one endof the current sharing bus is electrically connected to the feedbackcontrol circuit. The power converter adjusts an output current valuethereof in accordance with the current compensation value.

According to a further embodiment of the present invention, the powersystem comprises a voltage sharing bus, a current sharing bus, a masterpower supply unit, and at least a slave power supply unit. The voltagesharing bus is used to transmit a sharing voltage. The current sharingbus is used to transmit a first current reference value. The masterpower supply unit is used to provide power to a loading and provide thefirst current reference value. The at least one slave power supply unitare electrically connected in parallel with the master power supply unitand used to provide power to the at least one loading. The master powersupply unit comprise a first power converter, a first feed-forwardcontrol circuit, and a first feedback control circuit. The first powerconverter is electrically connected to a first power source and theloading. The first feed-forward control circuit is used to generate asecond current reference value in accordance with the difference betweenthe sharing voltage and a first input voltage of the power converter.The first feedback control circuit is used to generate the first currentreference value, and generate a first current compensation value inaccordance with a first output voltage of the first converter and thesecond current reference value. Then the first power converter adjusts afirst output current value thereof in accordance with the first currentcompensation value. Each of the slave power supply units comprises asecond power converter, a second feed-forward control circuit, and asecond feedback control circuit. The second power converter iselectrically connected to a second power source and the loading. Thesecond feed-forward control circuit is used to generate a third currentreference value in accordance with the difference between the sharingvoltage and a second input voltage of the second power converter. Thesecond feedback control circuit is used to generate a second currentcompensation value in accordance with the first current reference valueand the third current reference value. The second power converteradjusts a second output current value thereof in accordance with thesecond current compensation value.

According to a further embodiment of the present invention, the powersystem comprises a voltage sharing bus, a first power supply unit, and asecond power supply. The voltage sharing bus is used to transmit asharing voltage. The first power supply unit is used to provide power toa loading. The second power supply unit is used to provide power to theloading and electrically connected in parallel with the first powersupply. The first power supply comprises a first power converter, afirst resistor, and a first comparator. The first power converter iselectrically connected to a first power source and the loading, whereinthe first power converter comprises a first current output terminal anda first voltage reverence terminal, and the first current outputterminal is electrically connected to the loading. The first resistor iselectrically connected to a first input terminal of the first powerconverter. The first comparator is used to generate a first voltagecompensation value in accordance with the difference between the sharingvoltage and a first input voltage of the first power converter, whereinthe first comparator is electrically connected to the second resistorand the input terminal, and one end of the voltage sharing bus iselectrically connected between the first resistor and the firstcomparator. The first power converter adjusts a first output voltagethereof in accordance with the first voltage compensation value. Thesecond power supply unit comprises a second power converter, a secondresistor, and a second comparator. The second power converter iselectrically connected to a first power source and the loading, whereinthe second power converter comprises a second current output terminaland a second voltage reverence terminal, the second current outputterminal is electrically connected to the first voltage referenceterminal. The second resistor is electrically connected to a secondinput terminal of the second power converter. The second comparator isused to generate a second voltage compensation value in accordance withthe difference between the sharing voltage and a second input voltage ofthe second power converter, wherein the second comparator iselectrically connected to the second resistor and the second inputterminal, and another end of the voltage sharing bus is electricallyconnected between the second resistor and the second comparator. Thesecond power converter adjusts a second output voltage thereof inaccordance with the second voltage compensation value.

Therefore, with the application of the power system disclosed in theembodiments of the present invention, the converters are adapted toself-regulate the output current (or output voltage) supplied to theloading respectively according to the input status of each the powersources, thereby enhancing the power efficiency and life time of thepower system.

DESCRIPTION OF DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a system block diagram showing a conventional central powersystem;

FIG. 2 is a system block diagram showing a conventional distributedpower system; and

FIG. 3 is a system block diagram showing a power system according to afirst embodiment of the present invention;

FIG. 4 is a circuit diagram power supply unitaccording to a firstembodiment of the present invention;

FIG. 5 is a circuit diagram showing one power system according to thefirst embodiment of the present invention;

FIG. 6 is a circuit diagram showing one power supply unit of a powersystem according to the first embodiment of the present invention;

FIG. 7 is a system block diagram showing a power system according to asecond embodiment through a fifth embodiment of the present invention;

FIG. 8 shows several methods of using current sharing buses according toa second embodiment through a fifth embodiment of the present invention;

FIG. 9 is a circuit diagram showing one power supply unit of a powersystem according to the second embodiment of the present invention;

FIG. 10 is a circuit diagram showing a power system according to thesecond embodiment of the present invention;

FIG. 11 is a circuit diagram showing the power system according to thesecond embodiment of the present invention;

FIG. 12 is a circuit diagram showing a power system according to thesecond embodiment of the present invention;

FIG. 13 is a circuit diagram showing one power supply unit of a powersystem according to a third embodiment of the present invention;

FIG. 14 is a circuit diagram showing a power system according to a thirdembodiment of the present invention;

FIG. 15 is a circuit diagram showing the power system according to thethird embodiment of the present invention;

FIG. 16 is a circuit diagram showing a power system according to thethird embodiment of the present invention;

FIG. 17 is a circuit diagram showing one power supply unit of a powersystem 1300 according to a fourth embodiment of the present invention;

FIG. 18 is a circuit diagram showing a power system according to thefourth embodiment of the present invention;

FIG. 19 is a circuit diagram showing the power system according to thefourth embodiment of the present invention;

FIG. 20 is a circuit diagram showing a power system according to thefourth embodiment of the present invention;

FIG. 21 is a circuit diagram showing one power supply unit of a powersystem according to a fifth embodiment of the present invention;

FIG. 22 is a circuit diagram showing a power system according to thefifth embodiment of the present invention;

FIG. 23 is a circuit diagram showing a power system according to thefifth embodiment of the present invention;

FIG. 24 is a circuit diagram showing the power system according to thefifth embodiment of the present invention;

FIG. 25 is a circuit diagram showing a power system according to a sixthembodiment of the present invention; and

FIG. 26 is a circuit diagram showing a power system according to thesixth embodiment of the present invention.

BEST MODE

In order to make the illustration of the present invention more explicitand complete, the following description is stated with reference to FIG.3 through FIG. 26.

Referring to FIG. 3. FIG. 3 is a system block diagram showing a powersystem according to a first embodiment of the present invention. A powersystem 100comprises a plurality of power supply units 110, a sharing bus120 and at least one loading 130. Each of the power supply units 110comprises a power source 140, a power converter 150, and a convertercontrol circuit 160. The sharing bus 120 is electrically connected tothe converter control circuit 160 of each of the power supply units 110for sharing voltage signal, wherein the sharing bus 120 is a voltagesharing bus. The power source 140of the power system 100may be DC or ACpower sources, such as manpower generators, solar cells, fuel cells,wind-power generators, thermal-power generators, water-power generators,conventional electric power generators or electric cell, to input asource voltage to the power converter 150, thereby supplying power tothe loading 130 via the power converter 150.Thepower converter 150 maybe DC-to-DC, DC-to-AC, AC-to-DC or AC-to-AC converter for converting theinput voltage (DC or AC) to the output voltage (DC or AC). The loading130 may be any device or apparatus actuated by electric power, such as amotor. Furthermore, a single loading 130 or more than two loadings 130may be used in the power system 100.

Referring to FIG. 4. FIG. 4 is a circuit diagram showing one powersupply unit 110according to the first embodiment of the presentinvention. The converter control circuit 160comprises a resistor 160 a,and a first comparator 160 b.The resistor 160 a is electricallyconnected to the input terminal P, of the power converter 150 thus thatthe input voltage of the power converter 150 is inputted into thesharing bus 120 via the resistor 160 a. One end of the sharing bus 120is electrically connected between the resistor 160 a and the firstcomparator 160 b. The first comparator 160 b is used to generate acurrent reference value in accordance with the difference between theinput voltage of the power converter 150 and a sharing voltage. Thesharing voltage is the average of the input voltages inputted into thesharing bus 120 multiplied by weighted values. The power converter 150comprise a an another converter control circuit 152, wherein theconverter control circuit 152 can adjust the output thereof inaccordance with the current reference value. In addition, in thisembodiment the first comparator 160 b and the second comparator 160 dare more prefer op amplifiers. The power converter of this invention maycomprise electrical isolation elements (such as a transformer) orelectrical non-isolation elements, thus that the ground voltage GND1 isnot necessarily equal to the ground voltage GND2.

In view of the above description, the output current of the converter150can follow the difference between the voltage provided by the powersource 140 and the sharing voltage transmitted by the sharing bus 120.

Referring to FIG. 5. FIG. 5 is a circuit diagram showing a power system200 according to the first embodiment of the present invention. Thepower system 200 is a specific example of the power system 100. Thepower system 200 comprises a power supply unit 110 a, a power supplyunit 110 b, the sharing bus 120, and the loading 130, wherein the powersupply unit 110 a and power supply unit 110 b is similar to the powersupply unit 110. One end of the sharing bus 120 is electricallyconnected between the resistor 160 a and the first comparator 160 b ofthe power supply unit 110 a, and another end of the sharing bus 120 iselectrically connected between the resistor 160 a and the firstcomparator 160 b of the power supply unit 110 b. In the power system200, the power source 140 a provides a first voltage, and the powersource 140 b provides a second voltage, wherein the first voltage ishigher than the second voltage. When the first voltage (such as 48V) ishigher than the second voltage (such as 38V), the power supply unit 110a can output more current than that outputted by the power supply unit110 b and keep the power supply unit 110 b do not output the currentvalue exceeding the limitation thereof so that the power supply unit 110b is protected thereby.

Referring to FIG. 6. FIG. 6 is a circuit diagram showing one powersupply unit 310of a power system 300 according to the first embodimentof the present invention. The power system 300 comprises a plurality ofpower supply units 310. One power supply unit 310 is similar to thepower supply unit 110, but the difference is in that the power supplyunit 310 further comprises a current detector 160 c, a second comparator160 d, and an adder 160 e . The current detector 160 c is electricallyconnected to the output terminal Po of the power converter 150 to detectan output current value of the power converter 150. The adder 160 e isused to calculate the sum of the voltage compensation value and apredetermined voltage Vref, wherein the predetermined voltage Vref is acomparing level. The second comparator 160 d is used to generate acurrent compensation value in accordance with the difference between thesum and the output current value detected by the current detector 160 c,and then the power converter 150 adjusts the output current thereof inaccordance with the current compensation value..

Referring to FIG. 7 and FIG. 8, FIG. 7 is a system block diagram showinga power system 400 according to a second embodiment through a fifthembodiment of the present invention; and FIG. 8 shows several methods ofusing current sharing buses according to a second embodiment through afifth embodiment of the present invention. The power system 400comprises a plurality of power supply units 410, a voltage sharing bus420 a, a current sharing bus 420 b, and at least one loading 430. Eachof the power supply units 410 comprises a power source 440, a powerconverter 450, a feed-forward control (FFC) circuit 460, and a feedbackcontrol (FBC) circuit 470. The voltage sharing bus 420 a is electricallyconnected to the FFC circuit 460 of each of the power supply units 410,and the current sharing bus 420 b is electrically connected to the FBCcircuit 470 of each of the power supply units 410.

The power source 440 may be DC or AC power sources, such as manpowergenerators, solar cells, fuel cells, wind-power generators,thermal-power generators, water-power generators, conventional electricpower generators or electric cell, to input the input voltage to thepower converter 450, thereby supplying power to the loading 430 via thepower converter 450. The converters 450 may be DC-to-DC, DC-to-AC,AC-to-DC or AC-to-AC converter for converting the input voltage (DC orAC) to the output voltage (DC or AC). The loading 430 may be any deviceor apparatus actuated by electric power, such as a motor. Furthermore, asingle loading or more than two loadings may be used in the power system400.

In accordance with the second embodiment, the current sharing bus 420 bmay be connected by using the method such as dedicated master (DM)method, average current (AC) method, automatic master (AM) method orother suitable method, and the sharing control method may be an innerloop regulation (ILR), an outer loop regulation (OLR), a dual loopregulation (DLR), a single loop regulation (SLR) or other suitablemethod.

Referring to FIG. 9. FIG. 9 is a circuit diagram showing one powersupply unit 510 of a power system 500 according to the second embodimentof the present invention. Power system 500 comprises a plurality ofpower supply units 510, a voltage sharing bus 520 a, a current sharingbus 520 b, and at least one loading 530. Each of the power supply units510 comprises a power source 540, a power converter 550, a FFC circuit560, and a FBC circuit 570. The FFC circuit 560 comprises a resistor 560a and a first comparator 560 b, and the FBC circuit 570 comprises asecond comparator 570 a, a diode 570 b, an adder 570 c, a currentdetector 570 d, and a third comparator 570 e.In the power system 500,the current sharing bus 520 b is connected in theDM method and the innerloop regulation (ILR) is employed in the power system 500.

In the FFC circuit 560, the resistor 560 a is connected to the inputterminal P, of the power converter 550 thus that the input voltage ofthe power converter 550 is inputted into the voltage sharing bus 520 avia the resistor 560 a. One end of the voltage sharing bus 520 a iselectrically connected between the resistor 560 a and the firstcomparator 560 b. The first comparator 560 b generates a first currentreference value in accordance with the difference between the inputvoltage of the power converter 550 and a sharing voltage. The sharingvoltage is the average of the input voltages inputted into the sharingbus 520 a multiplied by weighted values.

In the FBC circuit 570, the second comparator 570 a generates a secondcurrent reference value in accordance with the difference between apredetermined voltage Vref and the output voltage of the power converter550, and forms a regulation loop RL. The positive terminal of the diode570 b is electrically connected to the second comparator 570 a, and thenegative terminal of that is electrically connected to the currentsharing bus 520 b, wherein the diode 570 b is used for automatic mastermethod (AM). In each of the power supply units 510, the second currentreference value may be inputted into the current sharing bus 520 b viathe diode 570 b so that the current sharing bus 520 b can transmitted athird current reference value automatically selected from all the secondcurrent reference value. The adder 570 c is used to add the firstcurrent reference value and the third current reference value togetherto generate a total current reference value, and the current detector570 d is electrically connected to the output terminal Po of the powerconverter 550 to detect the output current value of the power converter550. The third comparator 570 e is used to generate a currentcompensation value in accordance with the difference between the outputcurrent value of the power converter 550 and the total current referencevalue, wherein the third comparator 570 e and the current detector 570 dform a current sharing loop CSL. Then the power converter 550 adjuststhe output current thereof in accordance with the current compensationvalue. The current sharing loop CSL is formed prior to the regulationloop RL, thereby forming the inner loop regulation (ILR). In addition,in the power system 500, the first comparator 560 b, thesecondcomparator570 a, and the third comparator 570 e are more prefer op amplifiers.

In view of the above description, the output current of the converter550 can follow the voltage provide by the current sharing bus 520 b andthe difference between the voltage provided by the power source 540 andthe sharing voltage transmitted by the voltage sharing bus 520 a.

Referring to FIG. 10. FIG. 10 is a circuit diagram showing a powersystem 600according to the second embodiment of the present invention.The power system 600 is a specific example of the power system 500. Thepower system 600 comprises a power supply unit 510 a, a power supplyunit 510 b, a voltage sharing bus 520 a, a current sharing bus 520 b,and a loading 530, wherein the power supply unit 510 a and the powersupply unit 510 b are similar to the power supply unit 510. One end ofthe voltage sharing bus 520 a is electrically connected between theresistor 560 a and the first comparator 560 b of the power supply unit510 a, and another end of the voltage sharing bus 520 a is electricallyconnected between the resistor 560 a and the first comparator 560 b ofthe power supply unit 510 b.One end of the current sharing bus 520 b iselectrically connected between the diode 570 b and the adder 570 c ofthe power supply unit 510 a, and another end of the current sharing bus520 b is electrically connected between the diode 570 b and the adder570 c of the power supply unit 510 b . In the power system 600, thepower source 540 a is used to provide a first voltage and the powersource 540 b is used to provide a second voltage, and the first voltageis higher than the second voltage. For example, when the first voltage(such as 48V) provided is higher than the second voltage (such as 38V),the FFC circuit 560 of the power supply unit 510 a and that of the powersupply unit 510 b enable the output current value of the power supplyunit 510 a to be always higher than that of the power supply unit 510 b,and keep the output current of the power supply unit 510 b lower thanthe limitation thereof, thus that the power supply unit 510 b isprotected, and a output current difference between the power supply unit510 a and the power supply unit 510 b in the power system 600 is smallerthan that between the power supply unit 110 a and the power supply unit110 b in the power system 200.

Referring to FIG. 11. FIG. 11 is a circuit diagram showing a powersystem 700 according to the second embodiment of the present invention.The power system 700 is similar to the power system 500, but thedifference is in that each of the power supply units 710 of the powersystem 700 comprises a resistor 570 g instead of the diode 570 b.In thepower system 700, the average current (AC) method and the inner loopregulation (ILR) are employed, thus that the third current referencevalue is the average of the second current reference values inputtedinto the current sharing bus 520 b multiplied by weighted values.

Referring to FIG. 12. FIG. 12 is a circuit diagram showing a powersystem 800 according to the second embodiment of the present invention.The power system 800 comprises a master power supply unit 810 a, atleast one slave power supply unit 810 b, the voltage sharing bus 520 a,the current sharing bus 520 b, and the loading 530. The master powersupply unit 810 a is similar to the power supply unit 510, but thedifference is in that the master power supply unit 810 a do not have thediode 570 b, and one end of the current sharing bus 520 b is connectedbetween the first comparator 570 a and the adder 570 c of the masterpower supply unit 810 a. In addition, the slave power supply unit 810 bis similar to the master power supply unit 810 a, but the difference isin that the slave power supply unit 810 b do not have the firstcomparator 570 a, and one end of the current sharing bus 520 b isconnected to the adder 570 c of the slave power supply unit 810 b.In thepower system 800, the dedicated master (DM) method and the inner loopregulation (ILR) is employed, thus that the third current referencevalue is the second current reference value provided by the firstcomparator 570 a of the master power supply unit 810 a.

Referring to FIG. 13. FIG. 13 is a circuit diagram showing one powersupply unit 910 of a power system 900 according to a third embodiment ofthe present invention. Power system 900 comprises a plurality of powersupply units 910, a voltage sharing bus 920 a, a current sharing bus 920b, and at least one loading 930. Each of the power supply units 910comprises a power source 940, a converter 950, a FFC circuit 960, and aFBC circuit 970. The FFC circuit 960 comprises a resistor 960 a and afirst comparator 960 b, and the FBC circuit 970 comprises a secondcomparator 970 a, a diode 970 b, an adder 970 c, a current detector 970d, and a third comparator 970 e. In the power system 900, the currentsharing bus 920 b is connected in the AM method and the outer loopregulation (OLR) is employed.

In the FFC circuit 960, the resistor 960 a is connected to the inputterminal P, of the power converter 950 thus that an input voltage of thepower converter 950 is inputted into the voltage sharing bus 920 a viathe resistor 960 a. One end of the voltage sharing bus 920 a iselectrically connected between the resistor 960 a and the firstcomparator 960 b. Thefirst comparator 960 b generates a first currentreference value in accordance with the difference between the inputvoltage of the power converter 950 and a sharing voltage. The sharingvoltage is the average of the input voltages inputted into the sharingbus 920 a multiplied by weighted values.

In the FBC circuit 970,the current detector 970 d is electricallyconnected to the output terminal Po of the power converter 950 to detectthe output current value of the power converter 950.The positiveterminal of the diode 970 b is electrically connected to the currentdetector 970 d, and the negative terminal of that is electricallyconnected to the current sharing bus 920 b, wherein the diode 970 b isused for automatic master method. In each of the power supply units 910,the output current value of the power converter 950 may be inputted intothe current sharing bus 920 b via the diode 970 b so that the currentsharing bus 920 b can transmit a second current reference valueautomatically selected from all the output current values inputted intothe current sharing bus 920 b.The second comparator 970 a generates athird current reference value in accordance with the difference betweenthe second current reference value and the output current of the powerconverter 950, and forms a current sharing loop CSL. The adder 970 c isused to add the first current reference value, the third currentreference value, and a predetermined voltage Vref to generate a totalcurrent reference value. The third comparator 970 e is used to generatea current compensation value in accordance with the difference betweenthe output voltage value of the power converter 950 and the totalcurrent reference value, forms a regulation loop RL. Then the powerconverter 950 adjusts the output current thereof in accordance with thecurrent compensation value. The regulation loop RL is formed prior tothe current sharing loop CSL, thereby forming the outer loop regulation(OLR). In addition, in the power system 900, the first comparator 960 b,the second comparator 970 a, and the third comparator 970 e are moreprefer op amplifiers.

In view of the above description, the output current of the converter950 can follow the voltage transmitted by the current sharing bus 920 band the difference between the voltage provided by the power source 940and the sharing voltage transmitted by the voltage sharing bus 920 a. Itis noted that the predetermined voltage is not necessary in the thirdembodiment.

Referring to FIG. 14. FIG. 14 is a circuit diagram showing a powersystem 1000 according to the third embodiment of the present invention.The power system 1000 is a specific example of the power system 900. Thepower system 1000 comprises a power supply unit 910 a, a power supplyunit 910 b, a voltage sharing bus 920 a, a current sharing bus 920 b,and a loading 930, wherein the power supply unit 910 a and the powersupply unit 910 b is similar to the power supply unit 910. One end ofthe voltage sharing bus 920 a is electrically connected between theresistor 960 a and the first comparator 960 b of the power supply unit910 a, and another end of the voltage sharing bus 920 a is electricallyconnected between the resistor 960 a and the first comparator 960 b ofthe power supply unit 910 b. One end of the current sharing bus 920 b iselectrically connected between the diode 970 b and the comparator 970 aof the power supply unit 910 a, and another end of the current sharingbus 920 b is electrically connected between the diode 970 b and thecomparator 970 a of the power supply unit 910 b. The function of thepower system 1000 is similar to that of the power system 600. Forexample, when a first voltage (such as 48V) provided by a power source940 a is higher than a second voltage (such as 38V) provided by a powersource 940 b, the FFC circuit 960 of the power supply unit 910 a andthat of the power supply unit 910 b enable the output current value ofthe power supply unit 910 a to be always higher than that of the powersupply unit 910 b and keep the output current of the power supply unit910 b lower than the limitation thereof, thus that the power supply unit910 b is protected, and a output current difference between the powersupply unit 910 a and the power supply unit 910 b in the power system900 is smaller than that between the power supply unit 910 a and thepower supply unit 910 b in the power system 200.

Referring to FIG. 15. FIG. 15 is a circuit diagram showing a powersystem 1100 according to the third embodiment of the present invention.The power system 1100 is similar to the power system 900, but thedifference is in that each of the power supply units 1010 of the powersystem 1000 comprises a resistor 970 g instead of the diode 970 b.In thepower system 1100, the average current method and the outer loopregulation are employed, thus that the second current reference value isthe average of the second current reference values inputted into thecurrent sharing bus 920 b multiplied by weighted values.

Referring to FIG. 16. FIG. 16 is a circuit diagram showing a powersystem 1200 according to the third embodiment of the present invention.The power system 1200 comprises a master power supply unit 1210 a, atleast one slave power supply unit 1210 b, the voltage sharing bus 920 a,the current sharing bus 920 b, and the loading 930. The master powersupply unit 1210 a is similar to the power supply unit 910, but thedifference is in that the master power supply unit 1210 a do not havethe first comparator 970 a and the diode 970 b, and one end of thecurrent sharing bus 920 b is connected to the current detector 970 d ofthe master power supply unit 1210 a. In addition, the slave power supplyunit 1210 b is similar to the power supply unit 910, but the differenceis in that the slave power supply unit 1210 b do not have the diode 970b, and one end of the current sharing bus 920 b is connected to thefirst comparator 970 a. In the power system 1200, the dedicated master(DM) method and the outer loop regulation (OLR) is employed, thus thatthe second current reference value is the output current value detectedby the current detector 970 d of the master power supply unit 1210 a.

Referring to FIG. 17. FIG. 17 is a circuit diagram showing one powersupply unit1310 of a power system 1300 according to a fourth embodimentof the present invention. Power system 1300 comprises a plurality ofpower supply units 1310, a voltage sharing bus 1320 a, a current sharingbus 1320 b, and at least one loading 1330. Each of the power supplyunits 1310 comprises a power source 1340, a converter 1350, a FFCcircuit 1360, and a FBC circuit 1370. The FFC circuit 1360 comprises aresistor 1360 a and a first comparator 1360 b, and the FBC circuit 1370comprises a second comparator 1370 a, a diode 1370 b, an adder 1370 c, acurrent detector 1370 d, and a third comparator 1370 e.In the powersystem 1300, the current sharing bus 1320 b is connected in the AMmethod method and the dual loop regulation (DLR) is employed in thepower system 1300.

In the FFC circuit 1360, the resistor 1360 a is connected to the inputterminal P, of the power converter 1350 thus that the input voltage ofthe power converter 1350 is inputted into the voltage sharing bus 1320 avia the resistor 1360 a. One end of the voltage sharing bus 1320 a iselectrically connected between the resistor 1360 a and the firstcomparator 1360 b. The first comparator 1360 b generates a first currentreference value in accordance with the difference between the inputvoltage of the power converter 1350 and a sharing voltage. The sharingvoltage is the average of the input voltages inputted into the sharingbus 1320 a multiplied by weighted values.

In the FBC circuit 1370, the second comparator 1370 a generates a secondcurrent reference value in accordance with the difference between apredetermined voltage Vref and the output voltage of the power converter1350, and forms a regulation loop RL. The current detector 1370 d iselectrically connected to the output terminal Po of the power converter1350 to detect an output current value of the power converter 1350. Thepositive terminal of the diode 1370 b is electrically connected to thecurrent detector 1370 d and the negative terminal of that iselectrically connected to the current sharing bus 1320 b, wherein thediode 1370 b is used for automatic master method. In each of the powersupply units 1310, a output current value of the converter 1350 may beinputted into the current sharing bus 1320 b via the diode 1370 b sothat the current sharing bus 1320 b can transmitted a third currentreference value automatically selected from all the output currentvalues of the power supply units 1310. The third comparator 1370 e isused to generate a fourth current reference value in accordance with thedifference between the third current reference value and the outputcurrent value of the power converter 1350. The adder 1370 c is used toadd the first current reference, the second current reference, and thefourth current reference value together to generate a currentcompensation reference value. Then the power converter 1350 adjusts theoutput current thereof in accordance with the current compensationvalue. The current sharing loop CSL and the regulation loop RL areconnected in parallel, thereby forming the dual loop regulation (DLR).In addition, in the power system 1300, the first comparator 1360 b, thesecond comparator1370 a, and the third comparator 1370 e are more preferop amplifiers.

In view of the above description, the output current of the converter1350 can follow the voltage transmitted by the current sharing bus 1320b, and the difference between the voltage provided by the power source1340 and the sharing voltage transmitted by the voltage sharing bus 1320a.

Referring to FIG. 18. FIG. 18 is a circuit diagram showing a powersystem 1400 according to the fourth embodiment of the present invention.The power system 1400 is a specific example of the power system 1300.The power system 1400 comprises a power supply unit 1410 a, a powersupply unit 1410 b, the voltage sharing bus 1320 a, a current sharingbus 1320 b, and the loading 1330, wherein the power supply unit 1410 aand the power supply unit 1410 b is similar to the power supply unit1310. The power source 1340 a is used to provide a first voltage, andthe power source 1340 b is used to provide a second voltage. One end ofthe voltage sharing bus 1320 a is electrically connected between theresistor 1360 a and the first comparator 1360 b of the power supply unit1410 a, and another end of the voltage sharing bus 1320 a iselectrically connected between the resistor 1360 a and the firstcomparator 1360 b of thepower supply unit 1410 b. One end of the currentsharing bus 1320 b is electrically connected between the diode 1370 band and the third comparator 1370 e of the power supply unit 1410 a, andanother end of the current sharing bus 1320 b is electrically connectedbetween the diode 1370 b and the third comparator 1370 e of the powersupply unit 1410 b. The function of the power system 1400 is similar tothat of the power system 1000. For example, when a first voltage (suchas 48V) provided by a power source 1340 a is higher than a secondvoltage (such as 38V) provided by a power source 1340 b, the FFC circuit1360 of the power supply unit 1410 a and that of the power supply unit1410 b enable the output current value of the power supply unit 1410 ato be always higher than that of the power supply unit 1410 b and keepthe output current of the power supply unit1410 b lower than thelimitation thereof, thus that the power supply unit1410 b is protected,and a output current difference between the power supply unit 1410 a andthe power supply unit 1410 b in the power system 1400 is smaller thanthat between the power supply unit 1410 a and the power supply unit 1410b in the power system 200.

Referring to FIG. 19. FIG. 19 is a circuit diagram showing a powersystem 1500 according to the fourth embodiment of the present invention.The power system 1500 is similar to the power system 1300, but thedifference is in that each of the power supply units 1510 of the powersystem 1500 comprises a resistor 1370 g instead of the diode 1370 b.Inthe power system 1500, the average current (AC) method and the dual loopregulation (DLR) are employed, thus that the third current referencevalue is the average of all the output current values detected by thecurrent detectors 1370 d multiplied by weighted values.

Referring to FIG. 20. FIG. 20 is a circuit diagram showing a powersystem 1600 according to the fourth embodiment of the present invention.The power system 1600 comprises a master power supply unit 1610 a, atleast one slave power supply unit 1610 b, the voltage sharing bus 1320a, the current sharing bus 1320 b, and the loading 1330. The masterpower supply unit 1610 a is similar to the power supply unit 1310, butthe difference is in that the master power supply unit 1610 a does nothave the third comparator 1370 e and the diode 1370 b, and one end ofthe current sharing bus 1320 b is connected to the current detector 1370d of the master power supply unit 1610 a. In addition, the slave powersupply unit 1610 b is similar to the power supply unit 1310, but thedifference is in that the slave power supply unit 1610 b do not have thediode 1370 b, and one end of the current sharing bus 1320 b is connectedto the third comparator 1370 e of the slave power supply unit 1610 b. Inthe power system 1600, the dedicated master (DM) method and the dualloop regulation (DLR) is employed, thus that the third current referencevalue is the output current value detected by the current detector 1370d of the master power supply unit 1610 a.

Referring to FIG. 21. FIG. 21 is a circuit diagram showing one powersupply unit 1710 of the power system 1700 according to a fifthembodiment of the present invention. Power system 1700 comprises aplurality of power supply units 1710, a voltage sharing bus 1720 a, acurrent sharing bus 1720 b, and at least one loading 1730. Each of thepower supply units 1710 comprises a power source 1740, a converter 1750,a FFC circuit 1760, and a FBC circuit 1770. The FFC circuit 1760comprises a resistor 1760 a and a first comparator 1760 b, and the FBCcircuit 1770 comprises a second comparator 1770 a, a diode 1770 b, anadder 1770 c, and a current detector 1770 d. In the power system 1700,the current sharing bus 1720 b is connected in the AM method and thesingle loop regulation (SLR) is employed in the power system 1700.

In the FFC circuit 1760, the resistor 1760 a is connected to the inputterminal P, of the power converter 1750 thus that the input voltage ofthe power converter 1750 is inputted into the voltage sharing bus 1720 avia the resistor 1760 a. One end of the voltage sharing bus 1720 a iselectrically connected between the resistor 1760 a and the firstcomparator 1760 b. The first comparator 1760 b generates a first currentreference value in accordance with the difference between the inputvoltage of the power converter 1750 and a sharing voltage. The sharingvoltage is the average of the input voltages inputted into the sharingbus 1720 a or the average of the input voltages inputted into thesharing bus 1720 a multiplied by weighted values.

In the FBC circuit 1770, the current detector 1770 d is electricallyconnected to the output terminal Po of the power converter 1370 todetect the output current value of the power converter 1350.The positiveterminal of the diode 1770 b is electrically connected to the currentdetector 1770 d and the negative terminal of that is electricallyconnected to the current sharing bus 1720 b, wherein the diode 1770 b isused for automatic master method. In each of the power supply units1710, the output current value of the power converter 1750 may beinputted into the current sharing bus 1720 b via the diode 1770 b sothat the current sharing bus 1720 b can transmitted a second currentreference value selected automatically from all the output currentvalues inputted into the current sharing bus 1720 b. The secondcomparator 1770 a generates a third current reference value inaccordance with the difference between the second current referencevalue and the output current value of the power converter 1750. Theadder 1770 c is used to add the first current reference and the thirdcurrent reference value together to generate a current compensationvalue. Then the power converter 1750 adjusts the output current thereofin accordance with the current compensation value. Because the powersystem does not comprise regulation loop RL, the single loop regulationis formed. In addition, in the power system 1700, the first comparator1760 b, the second comparator 1770 a, and the third comparator 1770 eare more prefer op amplifiers.

In view of the above description, the output current of the converter1750 can follow the voltage transmitted by the current sharing bus 1720b, and the difference between the voltage provided by the power source1740 and the sharing voltage transmitted by the voltage sharing bus 1720a.

Referring to FIG. 22. FIG. 22 is a circuit diagram showing a powersystem 1800 according to the fifth embodiment of the present invention.The power system 1800 is a specific example of the power system 1700.The power system 1800 comprises a power supply unit 1810 a, a powersupply unit 1810 b, the voltage sharing bus 1720 a, a current sharingbus 1720 b, and the loading 1730, wherein the power supply unit 1810 aand power supply unit 1810 b are similar to the power supply unit 1710.The power source 1740 a is used to provide a first voltage, and thepower source 1740 b is used to provide a second voltage. One end of thevoltage sharing bus 1720 a is electrically connected between theresistor 1760 a and the first comparator 1760 b of the power supply unit1810 a, and another end of the voltage sharing bus 1720 a iselectrically connected between the resistor 1760 a and the firstcomparator 1760 b of the power supply unit 1810 b.One end of the currentsharing bus 1720 b is electrically connected between the diode 1770 band the second comparator 1770 a of the power supply unit 1810 a, andanother end of the current sharing bus 1720 b is electrically connectedbetween the diode 1770 b and the second comparator 1770 a of the powersupply unit 1810 b.The function of the power system 1800 is similar tothat of the power system 1000. For example, when a first voltage (suchas 48V) provided by a power source 1740 a is higher than a secondvoltage (such as 38V) provided by a power source 1370 b, the FFC circuit1760 of the power supply unit 1810 a and that of the power supply unit1810 b enable the output current value of the power supply unit 1710 ato be always higher than that of the power supply unit 1810 b and keepthe output current of the power supply unit1810 b lower than thelimitation thereof, thus that the power supply unit1810 b is protected,and a output current difference between the power supply unit 1810 a andthe power supply unit 1810 b in the power system 1800 is smaller thanthat between the power supply unit 1810 a and the power supply unit 1810b in the power system 200.

Referring to FIG. 23. FIG. 23 is a circuit diagram showing a powersystem 1900 according to the fifth embodiment of the present invention.The power system 1900 is similar to the power system 1700, but thedifference is in that each of the power supply units 1910 of the powersystem 1900 comprises a resistor 1770 g instead of the diode 1770 b. Inthe power system 1900, the average current method and the single loopregulation (SLR) are employed, thus that the second current referencevalue is the average of all the output current values detected by thecurrent detectors 1770 d.

Referring to FIG. 24. FIG. 24 is a circuit diagram showing a powersystem 2000 according to the fifth embodiment of the present invention.The power system 2000 comprises a master power supply unit 2010 a, atleast one slave power supply unit 2010 b, the voltage sharing bus 1720a, the current sharing bus 1720 b, and the loading 1730. The masterpower supply unit 2010 a is similar to the power supply unit 910 a, butthe difference is in that the FBC circuit 970 of the master power supplyunit 2010 a does not comprises the second comparator 970 a and the diode970 b, wherein the current detector is used to detect the output currentof the power converter 950; the adder 970 c is used to add the firstcurrent reference value and a predetermined voltage Vref together togenerate a fifth current reference value; and third comparator 970 e isused to generate a current compensation value in accordance with thedifference between the fifth current reference value and the outputvoltage value of the power converter 950 of the master power supply unit2010 a. Then the power converter 950 of the master power supply unit2010 a adjusts the output current thereof in accordance with the currentcompensation value. In addition, one end of the current sharing bus 1720b is electrically connected to the current detector 970 d to transmitthe output current value of the power converter 950 of the master powersupply unit 2010 a. The slave power supply unit 2010 b is similar to thepower supply unit 1710, but the difference is in that the slave powersupply unit 2010 b do not have the diode 1770 b, and one end of thecurrent sharing bus 1720 b is connected to the second comparator 1770 a.In the power system 2000, the dedicated master method and single loopregulation is employed, thus that the second current reference value isthe output current value detected by the current detector 970 d of themaster power supply unit 2010 a.

Referring to FIG. 25. FIG. 25 is a circuit diagram showing a powersystem 2100 according to a sixth embodiment of the present invention.The power system 2100 comprises a power supply unit 2110 a, a powersupply unit 2110 b, a voltage sharing bus 2120, and at least a loading2130. The power supply unit 2110 a comprises a power source 2140, apower converter 2150 a, and a FFC circuit 2160, wherein the powerconverter 2150 a comprises a current output terminal and a voltagereference terminal, and the current output terminal is connected to theloading 2130 to provide power. The power supply unit 2110 b comprisesthe power source 2140, a power converter 2150 b, and the FFC circuit2160, wherein the power converter 2150 b comprises a current outputterminal and a voltage reference terminal. The current output terminalof the converter 2150 b is electrically connected to the voltagereference terminal of the converter 2150 a, and the voltage referenceterminal of the converter 2150 b is electrically connected to groundvoltage.

The FFC circuit 2160 comprises a resistor 2160 a, and a first comparator2160 b. Because the function of the FFC circuit 2160 of the power supplyunit 2110 a and that of the power supply unit 2110 b are the same, thefollowing description takes the FFC circuit 2160 of the power supplyunit 2110 a as an example for explanation. In the FFC circuit 2160 ofthe power supply unit 2110 a, the resistor 2160 a is connected to theinput terminal P, of the power converter 2150 a thus that the inputvoltage of the power converter 2150 a is inputted into the voltagesharing bus 2120 via the resistor 2160 a. One end of the voltage sharingbus 2120 is electrically connected between the resistor 2160 a and thefirst comparator 2160 b. The first comparator 2160 b generates a voltagecompensation value in accordance with the difference between the inputvoltage of the power converter 2150 a and a sharing voltage. The sharingvoltage is the average of the input voltages inputted into the sharingbus 2120 multiplied by weighted values. Then the power converter 2150 aadjusts the output voltage Vo thereof in accordance with the voltagecompensation value.

In the power system 2100, the power source 2140 of the power supply unit2110 a provides a first voltage, and the power source 2140 of the powersupply unit 2110 b provides a second voltage, wherein the first voltageis higher than the second voltage. The function of the power system 2100is described in the followings. For example, when the first voltage(such as 48V) is higher than the second voltage (such as 38V), the FFCcircuit 2160 of the power supply unit 2110 a and that of the powersupply unit 2110 b enable the output voltage value of the power supplyunit 2110 a to be always higher than that of the power supply unit 2110b so that the power supply unit 2110 b do not output the voltageexceeding the limitation thereof.

Referring to FIG. 26. FIG. 26 is a circuit diagram showing a powersystem 2200 according to the third embodiment of the present invention.The power system 2200 is similar to the power system 2100, but thedifference is in that the power system 2200 further comprise a thirdpower supply unit 2110. The third power supply unit 2110 c is similar tothe first power supply unit 2110 a, but the difference is in that thecurrent output terminal of the power converter 2150 c is electricallyconnected to the voltage reference terminal of the power converter 2150a, and the voltage reference terminal of the power converter 2150 c iselectrically connected to the current output terminal of the powerconverter 2150 b. Because the advantages of the power system 2200 aresimilar to the power system 2100, the advantages of the power system2200 are not described here. In addition, the amount of the third powersupply unit is not limited here, connecting every two adjacent ones ofthe third power supply units can achieve the same advantages with thatof the power system 2200.

In view of the above description, the output current of the converter2150 can follow the difference between the voltage provided by the powersource 2140 and the sharing voltage transmitted by the voltage sharingbus 2120.

Therefore, the power system shown in the respective embodiments of thepresent invention provide a plurality of power sources connected inparallel or serial, so as to prevent the whole power system from notworking when a single power source is poor or fails. Further, theconverters are adapted to self-regulate the output current (or outputvoltage) supplied to the loading respectively according to the inputstatus of each the power sources, i.e. the power source with higherinput status can supply more power to the loading, and the power sourcewith lower input status can avoid supplying too much power, therebyenhancing the power efficiency and life time of the power system.

As is understood by a person skilled in the art, the foregoingembodiments of the present invention are strengths of the presentinvention rather than limiting of the present invention. It is intendedto cover various modifications and similar arrangements included withinthe spirit and scope of the appended claims, the scope of which shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar structure.

1. A power system, comprising: a voltage sharing bus used to transmit asharing voltage; and a plurality of power supply units electricallyconnected in parallel and used to provide power to a loading, whereineach of the power supply units is electrically connected to the voltagesharing bus to receive the sharing voltage, and comprises: a powerconverter electrically connected to a power source and the loading; aresistor electrically connected to a input terminal of the powerconverter; a first comparator used to generate a current reference valuein accordance with the difference between the sharing voltage and aninput voltage of the power converter, wherein the first comparator iselectrically connected to the resistor and the input terminal, and oneend of the voltage sharing bus is electrically connected between theresistor and the first comparator; a current detector used to detect anoutput current value of the power converter; and a second comparatorused to generate the current compensation value in accordance with thedifference between the output current value and the current referencevalue thus that the power converter adjusts the output current valuethereof in accordance with the current compensation value.
 2. The powersystem as claimed in claim 1, wherein each of the power supply unitsfurther comprises an adder electrically connected between the powerconverter and the second comparator, wherein the adder is used to addthe current reference value and a predetermined voltage value together.3. The power system as claimed in claim 1, wherein the sharing voltageis the average of the input voltages of the power converters multipliedby a plurality of weighted values.
 4. The power system as claimed inclaim 1, wherein the power source is a manpower generator, a solar cell,a fuel cells, a wind-power generator, a thermal-power generator, awater-power generator, a electric power generator and a electric cell.5. A power system, comprising: a voltage sharing bus used to transmit asharing voltage; a current sharing bus used to transmit a first currentreference; and a plurality of power supply units electrically connectedin parallel and used to provide power to a loading, wherein the powersupply units are electrically connected to the voltage sharing bus toreceive the sharing voltage and electrically connected to the currentsharing bus to receive the first current reference value, and each ofthe power supply units comprises: a power converter electricallyconnected to a power source and the loading; a feed-forward control(FFC) circuit used to generate a second current reference value inaccordance with the difference between the sharing voltage and an inputvoltage of the power converter, wherein one end of the voltage sharingbus is electrically connected to the feed-forward control circuit; and afeedback control (FBC) circuit used to generate a current compensationvalue in accordance with the first current reference value and thesecond current reference value, wherein one end of the current sharingbus is electrically connected to the feedback control circuit; whereinthe power converter adjusts an output current value thereof inaccordance with the current compensation value.
 6. The power system asclaimed in claim 5, wherein the feed-forward control circuit comprises:a resistor electrically connected to a input terminal of the powerconverter; and a first comparator used to generate the second currentreference value in accordance with the difference between the sharingvoltage and an input voltage of the power converter, wherein the firstcomparator is electrically connected to the resistor and the inputterminal, and one end of the voltage sharing bus is electricallyconnected between the resistor and the first comparator.
 7. The powersystem as claimed in claim 8, wherein the feedback control circuitcomprises: a first comparator used to generate a third current referencevalue in accordance with the difference between a output voltage of theconverter and a predetermined voltage; a diode, wherein a positiveterminal of the diode is electrically connected to the first comparatorand a negative terminal of the diode is electrically connected to theend of the current sharing bus; an adder used to add the first currentreference value and the second current reference value together togenerate a total current reference value; and a current detector used todetect the output current value of the power converter; a secondcomparator used to generate the current compensation value in accordancewith the difference between the total current reference value and theoutput current value of the power converter.
 8. The power system asclaimed in claim 5, wherein the feedback control circuit comprises: afirst comparator used to generate a third current reference value inaccordance with the difference between a output voltage of the converterand a predetermined voltage; a resistor electrically connected betweenthe first comparator and the end of the current sharing bus; an adderused to add the first current reference value and the second currentreference value together to generate a total current reference value; acurrent detector used to detect the output current value of the powerconverter; a second comparator used to generate the current compensationvalue in accordance with the difference between the total currentreference value and the output current value of the power converter. 9.The power system as claimed in claim 5, wherein the feedback controlcircuit comprises: a current detector used to detect the output currentvalue of the power converter; a diode, wherein a positive terminal ofthe diode is electrically connected to the current detector and anegative terminal of the diode is electrically connected to the end ofthe current sharing bus; a first comparator electrically connected tothe current detector and the end of the current sharing bus, wherein thefirst comparator is used to generate a third current reference value inaccordance with the difference between output current value and thesecond current reference value; an adder used to add the third currentreference value and the second current reference value together togenerate a total current reference value; and a second comparator usedto generates the current compensation value in accordance with the totalcurrent reference value and the output current value of the powerconverter.
 10. The power system as claimed in claim 9, wherein the adderfurther adds a predetermined voltage to the sum of the third currentreference value and the second current reference value together.
 11. Thepower system as claimed in claim 5, wherein the feedback control circuitcomprises: a current detector used to detect the output current value ofthe power converter; a resistor, electrically connected between thecurrent detector and the end of the current sharing bus; a firstcomparator connected to the current detector and the end of the currentsharing bus, wherein the first comparator is used to generate a thirdcurrent reference value in accordance with the difference between outputcurrent value and the second current reference value; an adder used toadd the third current reference value and the second current referencevalue together to generate a total current reference value; and a secondcomparator used to generates the current compensation value inaccordance with the total current reference value and the output currentvalue of the power converter.
 12. The power system as claimed in claim11, wherein the adder further adds a predetermined voltage on the sum ofthe third current reference value and the second current reference valuetogether.
 13. The power system as claimed in claim 5, wherein thefeedback control circuit comprises: a current detector used to detectthe output current value of the power converter; a diode, wherein apositive terminal of the diode is electrically connected to the currentdetector and a negative terminal of the diode is electrically connectedto the end of the current sharing bus; a first comparator electricallyconnected to the current detector and the end of the current sharingbus, wherein the first comparator is used to generate a third currentreference value in accordance with the difference between the outputcurrent value of the converter and the first current reference value; asecond comparator used to generates a fourth current reference value inaccordance with the difference between the a output voltage value of theconverter and a predetermined voltage; and an adder used to add thesecond current reference value, the third current reference value, andthe fourth current reference value together to generate the currentcompensation value.
 14. The power system as claimed in claim 5, whereinthe feedback control circuit comprises: a current detector used todetect the output current value of the power converter; a diode, whereina positive terminal of the diode is electrically connected to thecurrent detector and a negative terminal of the diode is electricallyconnected to the end of the current sharing bus; a first comparatorelectrically connected to the current detector and the end of thecurrent sharing bus, wherein the first comparator is used to generate athird current reference value in accordance with the difference betweenthe output current value of the converter and the first currentreference value; and an adder used to add the second current referencevalue, and the third current reference value together to generate thecurrent compensation value.
 15. The power system as claimed in claim 5,wherein the feedback control circuit comprises: a current detector usedto detect the output current value of the power converter; a resistorelectrically connected between the current detector and the end of thecurrent sharing bus; a first comparator electrically connected to thecurrent detector and the end of the current sharing bus, wherein thefirst comparator is used to generate a third current reference value inaccordance with the difference between the output current value of theconverter and the first current reference value; and an adder used toadd the second current reference value, and the third current referencevalue together to generate the current compensation value.
 16. The powersystem as claimed in claim 5, wherein the sharing voltage is the averageof the input voltages of the power converters multiplied by a pluralityof weighted values.
 17. The power system as claimed in claim 5, whereinthe power source is a manpower generator, a solar cell, a fuel cells, awind-power generator, a thermal-power generator, a water-powergenerator, a electric power generator and a electric cell.
 18. A powersystem, comprising: a voltage sharing bus used to transmit a sharingvoltage; a current sharing bus used to transmit a first currentreference value; a master power supply unit used to provide power to atleast one loading and provide the first current reference value, whereinthe master power supply unit comprises: a first power converterelectrically connected to a first power source and the at least oneloading; a first feed-forward control (FFC) circuit used to generate asecond current reference value in accordance with the difference betweenthe sharing voltage and a first input voltage of the power converter;and a first feedback control (FBC) circuit used to generate the firstcurrent reference value, and generate a first current compensation valuein accordance with a first output voltage of the first converter and thesecond current reference value; wherein the first power converteradjusts a first output current value thereof in accordance with thefirst current compensation value; and at least one slave power supplyunit electrically connected in parallel with the and used to providepower to the at least one loading, wherein the slave power supply unitsare electrically connected to the voltage sharing bus to receive thesharing voltage and electrically connected to the current sharing bus toreceive the first current reference value, and each of the power supplyunits comprises: a second power converter electrically connected to asecond power source and the at least one loading; a second feed-forwardcontrol (FFC) circuit used to generate a third current reference valuein accordance with the difference between the sharing voltage and asecond input voltage of the second power converter; and a secondfeedback control (FBC) circuit used to generate a second currentcompensation value in accordance with the first current reference valueand the third current reference value; wherein the second powerconverter adjusts a second output current value thereof in accordancewith the second current compensation value.
 19. The power system asclaimed in claim 18, wherein the first feed-forward control circuitcomprises: a resistor electrically connected to a input terminal of thefirst power converter; and a first comparator used to generate thesecond current reference value in accordance with the difference betweenthe sharing voltage and a first input voltage of the first powerconverter, wherein the first comparator is electrically connected to theresistor and the input terminal, and one end of the voltage sharing busis electrically connected between the resistor and the first comparator.20. The power system as claimed in claim 18, wherein the secondfeed-forward control circuit comprises: a resistor electricallyconnected to a input terminal of the second power converter; and a firstcomparator used to generate the third current reference value inaccordance with the difference between the sharing voltage and a secondinput voltage of the second power converter, wherein the firstcomparator is electrically connected to the resistor and the inputterminal, and one end of the voltage sharing bus is electricallyconnected between the resistor and the first comparator.
 21. The powersystem as claimed in claim 18, wherein the first feedback controlcircuit comprises: a first comparator used to generate the first currentreference value in accordance with the difference between the outputvoltage of the first converter and a predetermined voltage; an adderused to add the first current reference value and the second currentreference value together to generate a total current reference value;and a current detector used to detect the output current value of thefirst power converter; a second comparator used to generate the firstcurrent compensation value in accordance with the difference between thetotal current reference value and the output current value of the powerconverter.
 22. The power system as claimed in claim 18, wherein thesecond feedback control circuit comprises: an adder used to add thefirst current reference value and the second current reference valuetogether to generate a total current reference value; and a currentdetector used to detect the output current value of the second powerconverter; a first comparator used to generate the second currentcompensation value in accordance with the difference between the totalcurrent reference value and the output current value of the powerconverter.
 23. The power system as claimed in claim 18, wherein thefirst feedback control circuit comprises: a current detector used todetect a output current value of the first power converter to generatethe first current reference value; a first comparator used to generatethe first current compensation value in accordance with the differencebetween the output voltage of the first converter and the second currentreference value.
 24. The power system as claimed in claim 18, whereinthe first feedback control circuit comprises: a current detector used todetect a output current value of the first power converter to generatethe first current reference value; an adder used to add the firstcurrent reference value and the second current reference value togetherto generate a total current reference value; and a first comparator usedto generate the first current compensation value in accordance with thedifference between the output voltage of the first converter and thesecond current reference value.
 25. The power system as claimed in claim18, wherein the second feedback control circuit comprises: a firstcurrent detector used to detect the second output current value of thesecond converter; a first comparator used to generate a fourth currentreference value in accordance with the difference between the firstcurrent reference value and the second output current value of thesecond power converter; an adder used to add the fourth currentreference value and the third current reference value together togenerate a total current reference value; and a second comparator usedto generate the second current compensation value in accordance with thedifference between the total current reference value and a second outputvoltage of the second power converter.
 26. The power system as claimedin claim 18, wherein the first feedback control circuit comprises: acurrent detector used to detect a output current value of the firstpower converter to generate the first current reference value; a firstcomparator used to generate a fourth current reference value inaccordance with the difference between the output voltage value of thefirst converter and a predetermined voltage value; and an adder used toadd the fourth current reference value and the second current referencevalue together to generate the first current compensation value.
 27. Thepower system as claimed in claim 18, wherein the second feedback controlcircuit comprises: a first current detector used to detect the secondoutput current value of the second converter; a first comparator used togenerate a fourth current reference value in accordance with thedifference between the first current reference value and the secondoutput current value of the second power converter; a second comparatorused to generate a fifth current reference value in accordance with asecond output voltage value of the second converter and a predeterminedvoltage value; and an adder used to add the fourth current referencevalue, fifth current reference value, and the third current referencevalue together to generate the second current compensation value. 28.The power system as claimed in claim 18, wherein the first feedbackcontrol circuit comprises: a current detector used to detect a outputcurrent value of the first power converter to generate the first currentreference value; a first comparator used to generate the first currentcompensation value in accordance with the difference between the firstoutput voltage of the first converter and the second current referencevalue.
 29. The power system as claimed in claim 18, wherein the firstfeedback control circuit comprises: a current detector used to detect aoutput current value of the first power converter to generate the firstcurrent reference value; an adder used to add the second currentreference value and a predetermined voltage together to generate a totalcurrent reference value; and a first comparator used to generate thefirst current compensation value in accordance with the differencebetween the output voltage of the first converter and the total currentreference value.
 30. The power system as claimed in claim 18, whereinthe second feedback control circuit comprises: a first current detectorused to detect the second output current value of the second converter;a first comparator used to generate a fourth current reference value inaccordance with the difference between the first current reference valueand the second output current value of the second power converter; andan adder used to add the fourth current reference value and the thirdcurrent reference value together to generate the second currentcompensation value.
 31. The power system as claimed in claim 18, whereinthe sharing voltage is the average of the input voltages of the powerconverters multiplied by a plurality of weighted values.
 32. The powersystem as claimed in claim 18, wherein the power source is a manpowergenerator, a solar cell, a fuel cells, a wind-power generator, athermal-power generator, a water-power generator, a electric powergenerator and a electric cell.
 33. A power system, comprising: a voltagesharing bus used to transmit a sharing voltage; a first power supplyunit used to provide power to a loading, wherein the first power supplyunit comprises: a first power converter electrically connected to afirst power source and the loading, wherein the first power convertercomprises a first current output terminal and a first voltage reverenceterminal, and the first current output terminal is electricallyconnected to the loading; a first resistor electrically connected to afirst input terminal of the first power converter; and a firstcomparator used to generate a first voltage compensation value inaccordance with the difference between the sharing voltage and a firstinput voltage of the first power converter, wherein the first comparatoris electrically connected to the second resistor and the input terminal,and one end of the voltage sharing bus is electrically connected betweenthe first resistor and the first comparator; wherein the first powerconverter adjusts a first output voltage thereof in accordance with thefirst voltage compensation value. a second power supply unit used toprovide power to the loading, wherein the second power supply unitcomprises: a second power converter electrically connected to a firstpower source and the loading, wherein the second power convertercomprises a second current output terminal and a second voltagereverence terminal, the second current output terminal is electricallyconnected to the first voltage reference terminal; a second resistorelectrically connected to a second input terminal of the second powerconverter; and a second comparator used to generate a second voltagecompensation value in accordance with the difference between the sharingvoltage and a second input voltage of the second power converter,wherein the second comparator is electrically connected to the secondresistor and the second input terminal, and another end of the voltagesharing bus is electrically connected between the second resistor andthe second comparator; wherein the second power converter adjusts asecond output voltage thereof in accordance with the second voltagecompensation value.
 34. The power system as claimed in claim 33, whereinthe power system further comprises: at least one third power supply unitelectrically connected between the first power supply unit and thesecond power supply unit to provide power to the loading, wherein thethird power supply unit is electrically connected to the voltage sharingbus, and adjusts a third output voltage thereof in accordance with thesharing voltage.
 35. The power system as claimed in claim 33, whereinthe sharing voltage is the average of the input voltages of the powerconverters multiplied by a plurality of weighted values.
 36. The powersystem as claimed in claim 33, wherein the power source is a manpowergenerator, a solar cell, a fuel cells, a wind-power generator, athermal-power generator, a water-power generator, a electric powergenerator and a electric cell.